Pros
Lockheed Martin is a Big Huge Defense Contractor. The upside is, you do get to work on some of the best jets in the world. The pay is okay for the industry, but only in terms of starting salaries. Benefits are average at best. The entire LM corporation is massive, and you have access to literally thousands of jobs in the database--but you have to do the legwork yourself, since HR is worse than useless.
Cons
Lockheed Martin is a Big Huge Defense Contractor, and LM has become their customer, namely the federal government. The bureaucracy is literally worse than the Pentagon, and the simplest new activity requires weeks of approval meetings from people who have no idea what your job is, and reams of paperwork to be shuffled away into impenetrable databases. The Security department is mostly populated by idiots, and trust in employees (including those with high security clearances) is nil. Raises are set by computer (despite what HR tells the managers to say every year), and average around 2%. Recognition is minimal unless you're part of the unassailable Diversity cult. Mindless processes abound, and the endless HR-mandated "training" courses would insult the intelligence of a coffee table, as well as being an insult to the integrity of 99.999% of the employees. The most common event in an LM engineer's life is to hear a bean-counter or paper-pusher saying, "You can't do that." The second most common event in an LM engineer's life is to hear a bean-counter or paper-pusher saying, "That's not my job." Upper management is clueless about day-to-day operations, and mostly interested in heading off bad press coverage.